diff -Naur opencomal-0.2.6/src/pdcexec.h opencomal-0.2.6.patched/src/pdcexec.h
--- opencomal-0.2.6/src/pdcexec.h	2002-09-17 12:20:06.000000000 -0400
+++ opencomal-0.2.6.patched/src/pdcexec.h	2017-12-10 18:11:31.222211188 -0500
@@ -10,7 +10,7 @@
 
 /* Line execution routines header file */
 
-extern void run_error(int error, char *s, ...);
+extern void run_error(int error, char *s, ...) __attribute__((noreturn));
 extern void exec_call(struct expression *exp, int calltype, void **result,
 		      enum VAL_TYPE *type);
 extern int exec_trap(struct comal_line *line);
diff -Naur opencomal-0.2.6/src/pdcmisc.h opencomal-0.2.6.patched/src/pdcmisc.h
--- opencomal-0.2.6/src/pdcmisc.h	2002-12-06 05:31:50.000000000 -0500
+++ opencomal-0.2.6.patched/src/pdcmisc.h	2017-12-10 18:06:37.942210691 -0500
@@ -13,7 +13,7 @@
 extern void my_nl(int stream);
 extern void my_put(int stream, char *buf, long len);
 extern void my_printf(int stream, int newline, char *s, ...);
-extern void fatal(char *s, ...);
+extern void fatal(char *s, ...) __attribute__((noreturn));
 extern void *my_reverse(void *root);
 extern void free_list(struct my_list *root);
 extern int exp_list_of_nums(struct exp_list *root);
